Clementines belong to the rue family (Rutaceae) and come originally from southern China. They are a cross between the mandarin (Citrus reticulata) and the Seville orange (Citrus auratium).

They are an easily peelable ("Easypeeler"), moderate-sized, ellipsoidal orange citrus fruit containing no or few seeds.

In addition to oranges, the group of citrus fruits, which are mainly cultivated in subtropical regions, also includes lemons, grapefruits, mandarins, limes and easypeelers. Easypeeler is the name given in particular to crosses between oranges and mandarins whose peel is very easy to remove.

Citrus fruits are berry fruit consisting of three layers:

the outer yellow/orange peel (exocarp, flavedo), the glands of which exude the essential oils, which produce the typical citrus odor

The degree of ripeness of citrus fruit is determined on the basis of three criteria:

by the ripeness index: this is determined by the Brix value, which is a measure of the sugar/acid ratio of the fruit. According to [7], citrus fruit with a Brix value of between 10 and 16 have good flavor.

by cutting at purchase: freshness is determined by cutting the fruit in half from the stem-end to the opposite end. If the fruit is withered at the stem-end, it must not be shipped.

by peel color: the color of the peel is not necessarily a reliable indicator of ripeness, but its surface gloss is.

Fungicides are diphenyl, orthophenylphenol (OPP) and thiabendazole (TBZ). Diphenyl can be recognized from its naphthalene-like odor. The fungicides primarily prevent blue and green molds, but they do impair flavor and indication of their use is mandatory.

Quality / Duration of storage

The presence of stem and green leaves on the product does not indicate impaired quality. Green leaves are a sign of freshness and should be regarded as promoting sales.

Experience has shown that it is the care taken with preparation of the fruit for shipping which very largely determines whether individual batches withstand the rigors of transport. Such preparation for shipping is carried out in packing houses. These include:

Post-ripening of green or unsatisfactorily colored fruit to achieve a salable peel color in ripening rooms.

Coating with a layer of wax and treatment with preservatives and marking accordingly.

Grading of the fruits by size (gaging), color and other external features.

Counting, weighing and packing. Marking each package with details of number of fruit, quality class, variety and origin.

Storage until shipment in cold stores.

Waxing to prevent loss of aroma and weight is required because the washing process removes the natural wax layer. The film of wax sprayed onto the peel only partially seals the pores so that the fruits are still able to respire.

Maximum duration of storage and transport is as follows:

Temperature

Rel. humidity

Max. duration of storage

Source

6 - 9°C

85%

12 weeks

[1]

4.4°C

not stated

2 - 4 weeks

[39]

Clementines are not suited to controlled atmosphere storage.

Intended use

Clementines are mainly intended for fresh consumption, although, in their countries of origin, they are also canned, processed to make jams and confectionery and used to produce drinks.

Figures

(Click on the individual Figures to enlarge them.)

Figure 1

Figure 2

Figure 3

Countries of origin

This Table shows only a selection of the most important countries of origin and should not be thought of as exhaustive.

Clementines are highly pressure- and impact-sensitive and appropriate care must therefore be taken during cargo handling. The cold chain must at all costs be maintained, since otherwise there is a risk of rapid spoilage.

In damp weather (rain, snow), the cargo must be protected from moisture, as there is otherwise a risk of premature spoilage.

Stowage factor

2.2 m3/t (12 kg fruit crates) [1]

The stowage factor depends very much on weight categories and the packaging units used.

Because of its considerable impact- and pressure-sensitivity, packages of this cargo must be secured in such a way that they are prevented from damaging each other. Spaces between packages or pallets must be filled, to prevent slippage or tipping. By selecting the correct packaging size or cargo unit (area module or area module multiple), holds can be tightly loaded (without spaces).

A written cooling order must be obtained from the consignor before loading is begun. This order must always be complied with during the entire transport chain.

The following Tables merely constitute an estimate of appropriate temperature ranges. Temperatures may deviate from these values, depending on the particular transport conditions.

Designation

Temperature range

Source

Travel temperature

approx. 6 - 9°C

[1]

The holds or containers must be appropriately precooled before loading is begun.

The pulp temperature should not be < 4°C or > 25 - 30°C as storage life and appearance are impaired outside this range. Fruits punctured for pulp temperature measurement must be discarded as they would rapidly spoil and infect the other fruit. The measured values should be recorded in all cases in order to preserve evidence.

The return air temperature must reach 7.5°C as quickly as possible and be maintained throughout the voyage.

The temperature of the supply air should not fall below 5.5°C, since otherwise chilling damage may occur. During loading, pulp temperature measurements must be performed continually.

Depending upon the species and variety, all citrus fruits are highly cold-sensitive. Grapefruit, lemons and limes are more susceptible to chilling damage than are oranges and mandarins, and late-ripening varieties are more temperature-sensitive than early varieties. While oranges can withstand temperatures of 5°C, more temperature-sensitive types should never be shipped below 10°C. Green citrus fruits require higher transport temperatures than do yellow; the higher is the acid content of the fruit, the greater is its cold-sensitivity.

Chilling damage is manifested in citrus fruits in particular by spots on the peel (brown dots on the peel), accompanied by a bitter taste and unpleasant odor, rot and cell wall collapse. The glossiness of the peel is lost and the albedo layer (inner layer of the peel), which is normally white, turns a dark color. When the fruit is divided up, the segments, which have a low juice content, break up and the whole fruit is glassy and soft. The severity of the chilling damage is determined not only by the extent to which the temperature has fallen beneath the limit, but also by the length of exposure to this temperature. Chilling damage does not generally occur in cold stores, but instead prior to cooling or after leaving the cold stores.

The addition of fresh air is extremely important as citrus fruit can start to ferment within a few hours due to anaerobic respiration (resulting in total loss of the fruit). If ventilation is inadequate, storage damage may occur, taking the form of a bitter flavor and peel scab.

They are living organs in which respiration processes predominate, because their supply of new nutrients has been cut off by separation from the parent plant.

Care of the cargo during the voyage must be aimed at controlling respiration processes (release of CO2, water vapor, ethylene and heat) in such a way that the cargo is at the desired stage of ripeness on reaching its destination. Inadequate ventilation may result in fermentation and rotting of the cargo as a result of increased CO2 levels and inadequate supply of atmospheric oxygen (see Ventilation).

In fresh fruit, metabolic processes continue even after harvesting. The fruit absorbs oxygen (O2) and excretes varying amounts of carbon dioxide (CO2) and ethylene (C2H4) as well as aromatic compounds during the ripening process.

If ventilation has been inadequate (frost) or has failed owing to a defect, life-threatening CO2 concentrations or O2 shortages may arise. Therefore, before anybody enters the hold, it must be ventilated and a gas measurement carried out. The TLV for CO2 concentration is 0.49 vol.%.

Levels of respiratory gases which promote ripening, such as ethylene as well as carbon dioxide, should be kept as low as possible. If ventilation is inadequate, storage damage, such as a bitter flavor and peel scab, may occur. The supply of fresh air must thus be constant in order to dissipate these gases.

Due to their high content of highly volatile essential oils (formic and acetic acid, ethanal, ethylene and the odor substance limonene), citrus fruits are in general a highly odor-contaminating cargo and must thus not be stowed or stored together with fruit, vegetables and other odor-sensitive foodstuffs. Meat, butter, eggs, fats and cheese are particularly prone to absorbing the citrus odor. Cold stores must therefore be carefully deodorized before different goods are transported on the next voyage. Wooden dunnage tainted with the citrus odor must not be reused for odor-sensitive goods.

Passive behavior

Clementines are highly odor-sensitive and must therefore not be stored together with odor-emitting products.

Clementines are highly sensitive to impact, being softer than other citrus fruits, and therefore also spoil more easily. Spoilage due to mold and rot occurs in particular when the peel of the fruit is injured. Injury to peel occurs in the event of careless harvesting and due to incorrect handling of packages. Such injury may also be a sign of excessively low temperatures or incorrect use of postharvest phytosanitary agents.

To prevent mechanical injury to the peel, attention must be paid to the filling level of the cartons. They should be filled only to the edge, since overfilling leads to bruising and thus to premature spoilage when the cartons are stacked. Bruises become soft and the squashed peel looks like "goose-pimples". The aroma of the fruit is also lost and the flavor becomes bitter and unpleasant.

If ventilation has been inadequate (frost) or has failed owing to a defect, life-threatening CO2 concentrations or O2 shortages may arise. Therefore, before anybody enters the hold, it must be ventilated and a gas measurement carried out. The TLV for CO2 concentration is 0.49 vol.%.

Blue mold rot or storage rot is the most feared storage disease of citrus fruits and is caused by two species of mold: green mold (Penicillium digitatum), which is of an olive-green color, and blue mold (Penicillium italicum), which is of a blue-green color. The fungal spores mainly penetrate through small injuries and initially form white, circular spots of fungal growth, which are subsequently covered from the center outwards with a green or blue-green sporulating layer. The peel becomes spongy, the pulp soft - a typical instance of wet rot. Development is optimal at 20 - 27°C; growth still flourishes at 10°C and comes to a standstill only at 4°C. Blue mold is transferred from fruit to fruit by contact.